Currently, for cutting tools, and members, such as wear-resistant members, and sliding members, requiring high wear resistance, slidability, and fracture resistance, a technique in which a coating layer is formed on the surface of a substrate made of a sintered alloy such as a cemented carbide alloy or a cermet, a sintered body having high hardness such as diamond or cubic boron nitride (cBN), or ceramics such as alumina or silicon nitride has been employed to improve the wear resistance, slidability, or fracture resistance.
Furthermore, coating layers made of nitride mainly composed of Ti and Al and formed using an ion plating method or sputtering method have been actively studied and continuously improved for extending the tool life. In addition to the coating material elements, these surface-coated tools have been variously contrived for corresponding to changes in the cutting environment, such as an increase in cutting speed, and diversification of work materials.
For example, Patent Documents 1 and 2 disclose coating films (coating layers) of a surface-coated tool having a surface of a substrate coated by TiAlN or the like by an ion plating method, the coating films having a Ti ratio that is made larger on a cutting edge than on a flat portion by increasing an absolute value of a negative bias applied during layer formation in a later formation stage more than in an initial formation stage.